Surgery, Biopsies and Chemotherapeutics Flashcards
Describe Marek disease virus
- Oncogenic herpesvirus
- Tumours derived from T lymphocytes
What are the consequences on immune cells due to Marek’s disease virus?
- B lymphocytes and macrophages are killed
- T-lymphocytes are activated to proliferate and form tumour
Outline the control of Marek’s disease virus
- Disinfection
- Biosecurity
- All-in, all-out management
- Vaccination
- New strains emerging each more virulent, so new vaccines required at each new mutation
Why is diagnosis and staging important prior to treatment of a tumour?
- Extent of treatment depends on tumour type and stage
- With regards to surgery, need to know the surgical margins that will be required
What are the general principles of biopsy?
- Handle tissue gently
- Position site within probable surgical or radiotherapy field
- Should be as small as possible, position so as to not increase size of treatment area
- Sample from different areas of lesion, including junction of normal-abnormal tissue
- Avoid local dissemination of neoplastic tissue
- So not breach anatomical planes
What are the indications for incision biopsy?
- When mass will not exfoliate well for FNA, not amenable to core biopsy
- When cytology or core biopsy results are non-diagnostic
- Lack of core biopsy equipment
- If is more likely to achieve diagnosis and grade
What are disadvantages of excisional biopsy?
- Surgical margins unknown, risky
What are the advantages of an excisional biopsy?
- May be cost saving in some cases
- Diagnosis and treatment are possible within single surgery
- Good where diagnosis of tumour type and grade will not affect surgical approach
What are the roles of oncological surgery?
- Prophylactic e.g. ovariohysterectomy prior to 1st season, cryptorchid testicles
- Diagnosis and staging
- Definitive excision
- Palliative surgery
- Cytoreduction in order to treat with adjunctive methods
- Management of oncologic emergencies
- Surgery for supportive therapy
- Treatment of metastatic disease
What are the 3 possible aims of surgical excision of a tumour?
- Curative
- Cytoreductive
- Palliative
What is meant by palliative surgical excision of a tumour?
Where removal of a tumour that is causing other problems e.g. blocking nasal passages
Compare primary surgery and revisions with regards to success in treating tumours
- Primary best chance for cure
- Untreated tumours have more normal surrounding anatomy facilitating surgical removal
- Recurrent tumours may have seeded to previously unaffected areas, need wider, deeper resection
What is meant by surgical dose?
How much surgery
What is marginal excision?
- Excision immediately outside the pseudocapsule
- Are leaving behind microscopic volumes of tumour
What is a wide excision?
Removal of tumour with complete margins of normal tissue in all directions, so local recurrence is unlikely
What tissues are good natural barriers to spread of cancer cells?
Collagen rich, relatively avascular tissues e.g. fascia, ligaments, tendons and cartilage
What tissues are poor barriers to spread of cancer?
Fat, subcutaneous tissue, muscle, other parenchymatous organs
What is radical excision?
Removal of entire anatomical structure or compartment continuing the tumour e.g. limb amputation, mastectomy. Local recurrence is unlikely
What is meant by lateral and deep margins of a tumour?
- Lateral are the margins around the visible lesion (ruler used)
- Deep margins are the margins below the visible lesion
In what lesions is a needle only FNA useful?
Soft masses and lymph nodes, want to avoid destroying fragile cells with suction
In what lesions is a continuous suction FNA useful?
Firm masses e.g. firbosarcomas as these do no exfoliate well
In what lesions is an intermittent suction FNA useful?
Small masses where it is not possible to redirect the needle without exiting the mass
What size needle should be used for FNAs?
23 gauge
What are the indications for a tru-cut biopsy?
- Superficial masses (incl. lymph nodes) that can be palpated and stabilised
- Internal organs that can be safely accessed via ultrasound guidance
What are the contra-indications for a tru-cut biopsy?
- Highly vascular structures
- Disorders of primary and secondary haemostasis
- Where structure to be biopsied cannot be stabilised
- Structure with thin wall that may leak contents following sampling
Describe the technique for tru-cut biopsy
- Under heavy sedation or GA
- Clean and aseptically prepare skin over area to be biopsied
- Small incision in skin
- Load needle, advance into sample area
- Once in, advance stylet to expose the biopsy notch
- Deploy cutting cannula by depressing the plunger
- Remove needle from mass
- Pull plunger back into lock position to remove sample
- Push stylet forwards to reveal notch with tissue
- Use fine needle to lift sample off and place in formalin
Describe the site preparation for a punch biopsy
- Sedate patient (or GA for ears, nose, toes)
- Clip with scissors to preserve skin
- Do not disturb crusts or skin surface, do not prep or scrub skin
- Draw orientation line along line of hair growth in indelible marker
- Draw circle around lesion
- Inject subcut local anaesthetic on this circle, advancing into each previous injection site
Outline the method of taking a punch biopsy
- Usually 6-9mm punch, as large as possible
- Hold perpendicular to skin surface
- Rotate in one direction only
- Do not reuse blunt biopsy punches
- Only through skin, check regularly
- Grasp sample by subcut tissue and cut connecting tissue
What can be used to stabilise thin biopsy samples?
Stiff card or wooden tongue depressor, to prevent warping of tissue
When should a wedge/ellipse biopsy be used?
- Excision of solitary nodules
- Transition from normal to lesional skin
- Vesicles
- Suspected deep lesions e.g. panniculitis
What is the common outcome of all chemotherapeutic drugs?
Prevent cellular division and subsequent cell death
Outline the common side effects of chemotherapeutics
- Major systems affected are GI and bone marrow
- Some drug specific side effects
- Renal and hepatic dysfunction
- Alopecia in some species/breeds (poodles, Bichon Frise, Old English Sheepdog)
- Not as severe in humans
What drugs are included in the COP protocol?
Cyclophosphamide, Vincristine, Prednisolone
What drugs are used in the COPH protocol?
Cyclophosphamide, Vincristine, Prednisolone and Doxorubicin
When are tyrosine kinase inhibitors indicated in cancer treatment?
Mast cell tumours
How do alkylating agents work?
Give an example of a drug in class and a cancer that it targets.
Alkyl group binds to DNA causing cross linkage
Example of drug - Cyclophosphamide, lymphoma
How do plant alkaloids work?
Give an example of a drug in class and a cancer that it targets.
Bind to tubulin in cells and disrupt the mitotic spindle.
Vincristine - Lymphoma and leukaemia
How do anti-metabolites work?
Give an example of a drug in class and a cancer that it targets.
Inhibit the use of cell metabolites used in growth and cell division.
Cytarabine - lymphoma
How do Anti tumour antibiotics work?
Give an example of a drug in class and a cancer that it targets.
Inhibit topoisomerase II causing breakage of DNA and cell death.
Doxorubicin - lymphoma
How do platinum analogues work?
Give an example of a drug in class and a cancer that it targets.
Bind platinum to DNA causing cross linkage and cell death.
Carboplatin - osteosarcoma and carcinomas
How do tyrosine kinase inhibitors work?
Give an example of a drug in class and a cancer that it targets.
Inhibit TK receptors.
Masitinib - Mast cell tumours
